The invention relates to a process for the preparation of copolymers of carbon monoxide and olefinically unsaturated compounds.
European Patent Application No. 0,460,743 discloses a process for the preparation of copolymers of carbon monoxide and one or more olefinically unsaturated compounds, which process comprises contacting the monomers at an elevated temperature and pressure in the presence of hydrogen and one or more aprotic polar diluents, such as tetrahydrofuran (THF) or methyl ethyl ketone. The most suitable catalyst is a catalyst composition comprising a Group VIII metal, preferably palladium, and a phosphorus bidentate ligand. The prior art teaches that this bidentate ligand forms a complex with the Group VIII metal and that the molar ratio of bidentate ligand to Group VIII metal should not exceed 1.5 and preferably should be about 1 in order to obtain optimum activity from the catalyst. Additionally, it was generally believed by those skilled in the art that at bidentate ligand/Group VIII metal molar ratios in excess of 1.5, most or all of the catalytically active sites of the Group VIII metal will form complexes with the phosphorus bidentate ligand. Although this improves the stability of the catalyst composition, it is detrimental to its catalytic activity.
It is an object of the present invention to provide a process for the preparation of copolymers of carbon monoxide and olefinically unsaturated compounds, wherein a stable catalyst composition comprising a Group VIII metal and a phosphorus bidentate ligand is used and wherein the copolymer is prepared at an excellent polymerization rate and with high selectivity.
Surprisingly, it has been found that excellent polymerization rates can be accomplished when using a catalyst composition comprising a phosphorus bidentate ligand and a Group VIII metal in a molar ratio of more than one in the presence of hydrogen.